/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlineGameMatchesInterface.h
Joins a player to an existing match
void JoinGameMatch ( const [FUniqueNetId](API\Runtime\CoreOnline\Online\FUniqueNetId) & UserId, const [FString](API\Runtime\Core\Containers\FString) & MatchId, const [TArray](API\Runtime\Core\Containers\TArray)< [FJoinGameMatchPlayer](API\Plugins\OnlineSubsystem\Interfaces\FJoinGameMatchPlayer) > & GameMatchJoinPlayerData, const [FOnJoinGameMatchComplete](API\Plugins\OnlineSubsystem\Interfaces\FOnJoinGameMatchComplete) & CompletionDelegate )